Conventionally, to unlock a lock with a key, a plurality of pins provided at the internal cylinder of the lock are driven by mechanical projections and recesses or a magnetic force by an embedded magnet formed at the insertion portion of the key body so that pins bridging over the boundary surface of the internal cylinder and the fixed external cylinder are moved, and the internal cylinder is rotated within the external cylinder. However, when a combination of a mechanical key and a lock is used, the lock can be unlocked, if a reproduced key has the same shape as that of an original key. In addition, it is difficult to make defensive structures against destructive activities with such combination. In particular, in case of keys for vehicles, since an engine starter can be operated by directly connecting electric wires without using the key, it is difficult to achieve complete key functions by use of a conventional combination of a key and a lock.
To solve this problem, in addition to the insertion portion of a key having mechanical projections and recesses or magnetic force generating portion, a key with a built-in transmitting element for transmitting a specified ID code has been proposed. According to an embodiment of such key, only when a receiving element installed in a vehicle receives the specified ID code, the engine of the vehicle can be started or continuously operated so that the movement of the vehicle due to a direct connection of electric wires or mechanical destruction can be prevented.
Since the transmitting element is required for such conditions that the transmitting element is small and metal portions are not disposed on the periphery of the transmitting element, the transmitting element is not generally disposed at the insertion portion of the key body, but at a grip portion (key knob) formed by non-metallic member such as resin which does not interfere in transmitting functions. Further, when a battery is exhausted, since the transmitting element cannot transmit the ID code and the vehicle engine cannot be started, a key with a built-in transmitting element which is not necessary for a battery has been adopted in recent years. However, since it is necessary to apply heat or pressure to form the grip portion with non-metallic member such as resin, there is such a problem that the transmitting element is damaged by the heat or the pressure. Further, since the grip portion is formed by non-metallic member such as resin, there is also such a problem that the transmitting element is damaged due to an external force applied to the transmitting element by rotating the key body.
Furthermore, since the grip portion is merely assembled with the key body, there is also such a problem that a gap between the grip portion and the key body may be formed by the external force applied to the key body.